Is there any chance water vapor from your shower is getting to the alarm?

We have a smoke detector located close to one of the bathrooms in our house, after several years of service the alarm sounds whenever we take a shower.

Running the vent fan in the bathroom eliminates the problem. I'm not sure if CO2 alarms can be sensitive to water vapor, anyway if your not running the bathroom vent fan when showering you might try turning it on and see if it helps.

CO alarms only last a limited period of time. I think it is 5 years. I had one that was erratic. I found it easier to replace although there is supposed to be a way to fix them. Cleaning didn't seem to help.

12 years old? think replacing would be good. Actually now that Im think about it our LP detector is original, its hard wired. I was unaware of hardwired CO detectors. Thought, like most smoke detectors, battery powered. Ive only seen hardwired that had battery backup on co/smoke detectors
I would still change out but wonder why pump triggers detector? Or failing detector more sensitive to low/fluctuating power. I know our pump caused our incandesants to flicker.